Abrasives are commonly used to grind, sand, and polish materials such as wood, metal, paint, and plastic. One method of abrading a workpiece is to affix an abrasive sheet to a backup pad, and to rotate the backup pad while urging the abrasive against a workpiece. In many applications, the abrasive sheet and the backup pad are circular, although other configurations are also known. For example, U.S. Pat. No. 4,920,702 (Kloss et al.) discloses a portable grinder having, in one embodiment, a generally triangular backup pad and abrasive sheet that are vibrated rather than rotated.
The abrasive sheet may be affixed to the backup pad in a number of different ways. For example, the use of a pressure sensitive adhesive (see, e.g., U.S. Pat. No. 3,849,949 (Steinhauser et al.)), interengaging fastener members, such as hook portions on the backup pad and loop fabric on the abrasive sheet (see, e.g., U.S. Pat. No. 4,609,581 (Ott)), loop fabric on the backup pad and hooks on the abrasive article (see, e.g., U.S. Pat. No. 5,672,186 (Chesley et al) and U.S. Pat. No. 5,692,949 (Sheffield et al)), intermeshing fasteners (see, e.g., U.S. Pat. No. 4,875,259 (Appeldorn) or U.S. Pat. No. 5,201,101 (Rouser et al.)), and cooperating male and female fastener members, are known in the art.
The backup pad may be configured to be hand held, or may be configured for attachment to a powered abrading apparatus. A typical abrading apparatus includes a rotating output shaft that is powered by an abrading head. These abrading apparatuses, alternatively referred to as grinders herein, may be electrically or pneumatically powered, and typically rotate the backup pad at speeds between 3,000 and 20,000 revolutions per minute. The abrading apparatus may be one of several types. For example, a rotary grinder simply rotates the backup pad and attached abrasive sheet about a fixed axis. A random orbital grinder combines a rotary and orbital motion that results in a random motion of the backup pad with respect to the abrading head.
The diameter of the abrasive sheet is typically larger than the diameter of the backup pad (for example, a 127 mm sheet and a 124 mm pad), to permit abrading near the periphery of the abrasive sheet without damage to the backup pad or to the surface being abraded. It is desirable to position the abrasive sheet relative to the backup pad so that the sheet extends beyond the backup pad around its entire circumference without any of the support surface of the backup pad exposed. It is also desirable to center the abrasive sheet relative to the backup pad so that the amount by which the sheet extends beyond the backup pad is relatively constant along the periphery of the sheet. Typically, the operator of the apparatus applies the abrasive sheet by hand while attempting to center it as well as possible. It is also known to program robotic sanders to attach abrasive sheets centered on the backup pad (see U.S. Pat. No. 5,377,455 (Lanzer)).
Various dispensers for abrasive articles are known, such as those disclosed in U.S. Pat. No. 3,849,949 (Steinhauser et al.) or WIPO International Patent Application Publication No. WO96/38264 (King et al.). However, these dispensers do not provide a convenient way to center an abrasive sheet on a backup pad.
It is desirable to provide an abrasive sheet dispenser that simply and effectively centers an abrasive sheet on a backup pad.